feat: Add goto type definition.

README.md

@@ -28,6 +28,7 @@ This is a language server for JavaScript and TypeScript that adheres to the [Lan
 
  - Hovers
  - Goto definition
+ - Goto type definition
  - Find all references
  - Document symbols
  - Workspace symbol search

src/test/typescript-service-helpers.ts

@@ -143,6 +143,8 @@ export function describeTypeScriptService(
                             'let target = i.target;',
                         ].join('\n'),
                     ],
+                    [rootUri + 'foo/f.ts', ['import {Foo} from "./b";', '', 'let foo: Foo = Object({});'].join('\n')],
+                    [rootUri + 'foo/g.ts', ['class Foo = {}', '', 'let foo: Foo = Object({});'].join('\n')],
                 ])
             )
         )
@@ -224,6 +226,68 @@ export function describeTypeScriptService(
                 ])
             })
         })
+
+        describe('textDocumentTypeDefinition()', function(this: TestContext & ISuiteCallbackContext): void {
+            specify('in other file', async function(this: TestContext & ITestCallbackContext): Promise<void> {
+                const result: Location[] = await this.service
+                    .textDocumentTypeDefinition({
+                        textDocument: {
+                            uri: rootUri + 'foo/f.ts',
+                        },
+                        position: {
+                            line: 2,
+                            character: 5,
+                        },
+                    })
+                    .reduce<Operation, Location[]>(applyReducer, null as any)
+                    .toPromise()
+                assert.deepEqual(result, [
+                    {
+                        uri: rootUri + 'foo/b.ts',
+                        range: {
+                            start: {
+                                line: 1,
+                                character: 13,
+                            },
+                            end: {
+                                line: 1,
+                                character: 16,
+                            },
+                        },
+                    },
+                ])
+            })
+            specify('in same file', async function(this: TestContext & ITestCallbackContext): Promise<void> {
+                const result: Location[] = await this.service
+                    .textDocumentTypeDefinition({
+                        textDocument: {
+                            uri: rootUri + 'foo/g.ts',
+                        },
+                        position: {
+                            line: 2,
+                            character: 5,
+                        },
+                    })
+                    .reduce<Operation, Location[]>(applyReducer, null as any)
+                    .toPromise()
+                assert.deepEqual(result, [
+                    {
+                        uri: rootUri + 'foo/g.ts',
+                        range: {
+                            start: {
+                                line: 0,
+                                character: 6,
+                            },
+                            end: {
+                                line: 0,
+                                character: 9,
+                            },
+                        },
+                    },
+                ])
+            })
+        })
+
         describe('textDocumentXdefinition()', function(this: TestContext & ISuiteCallbackContext): void {
             specify('on interface field reference', async function(
                 this: TestContext & ITestCallbackContext

src/typescript-service.ts

@@ -297,6 +297,7 @@ export class TypeScriptService {
                     triggerCharacters: ['(', ','],
                 },
                 definitionProvider: true,
+                typeDefinitionProvider: true,
                 referencesProvider: true,
                 documentSymbolProvider: true,
                 workspaceSymbolProvider: true,
@@ -362,15 +363,31 @@ export class TypeScriptService {
      */
 
     public textDocumentDefinition(params: TextDocumentPositionParams, span = new Span()): Observable<Operation> {
-        return this._getDefinitionLocations(params, span)
+        return this._getDefinitionLocations(params, span, false)
+            .map((location: Location): Operation => ({ op: 'add', path: '/-', value: location }))
+            .startWith({ op: 'add', path: '', value: [] })
+    }
+
+    /**
+     * The goto type definition request is sent from the client to the server to resolve the type
+     * location of a symbol at a given text document position.
+     *
+     * @return Observable of JSON Patches that build a `Location[]` result
+     */
+    public textDocumentTypeDefinition(params: TextDocumentPositionParams, span = new Span()): Observable<Operation> {
+        return this._getDefinitionLocations(params, span, true)
             .map((location: Location): Operation => ({ op: 'add', path: '/-', value: location }))
             .startWith({ op: 'add', path: '', value: [] })
     }
 
     /**
      * Returns an Observable of all definition locations found for a symbol.
      */
-    protected _getDefinitionLocations(params: TextDocumentPositionParams, span = new Span()): Observable<Location> {
+    protected _getDefinitionLocations(
+        params: TextDocumentPositionParams,
+        span = new Span(),
+        goToType = false
+    ): Observable<Location> {
         const uri = normalizeUri(params.textDocument.uri)
 
         // Fetch files needed to resolve definition
@@ -392,9 +409,9 @@ export class TypeScriptService {
                     params.position.line,
                     params.position.character
                 )
-                const definitions: ts.DefinitionInfo[] | undefined = configuration
-                    .getService()
-                    .getDefinitionAtPosition(fileName, offset)
+                const definitions: ts.DefinitionInfo[] | undefined = goToType
+                    ? configuration.getService().getTypeDefinitionAtPosition(fileName, offset)
+                    : configuration.getService().getDefinitionAtPosition(fileName, offset)
 
                 return Observable.from(definitions || []).map((definition): Location => {
                     const sourceFile = this._getSourceFile(configuration, definition.fileName, span)